Visual causes of dizziness
Some of the causes of pathological nystagmus, which is a visually-triggered form of dizziness, are highlighted in this article.
Unlike that Benign Paroxismal Positional Vertigo, other pathological forms of nystagmus could be contributing to feelings of dizziness, loss of balance, and fatigue associated with some patients.
These forms of dizziness can be due to a lack of adaption, or a slowness of adaption, of the visual senses and the associated vestibular and proprioceptive feedback loops that keep us upright.
Many types of vestibular feedback loops are present:
- Vestibular Ocular Reflex (VOR): this is the correction of the eye movements with regards to head movements.
- The abducent nerve and the vestibular system: The abducent nerve is cranial nerve VI and arises from the pons on the brain stem, and works with the oculomotor nerve (cranial nerve IV) for controlling eye movement.
- Saccades: A saccade is a very rapid eye movement, often called a saccadic correction clinically, and is a very rapid movement of up to 50-1000 angular degrees per second. This is a strategy we adapt for accuracy of limb movement. If the eyes are not able to complete the saccades at this rapid state, or are having additional movements, this will impact overall focus on a task and may cause dizziness.
- Agoraphobia: more than just not liking crowds or closed in places, those individuals who struggle with convergence of the eyes (being able to fixate on a target) may find these situations overwhelming, and report dizziness. While this disorder is often linked to a form of anxiety as well, further mechanical causes of symptoms should be examined.
- Acrophobia: the fear of heights can also trigger dizziness due to an inability to focus on a nearby target.
- Superior Rectus: The Superior Rectus (SR) is a muscle of the eye that helps focus on a target. Often people with dizziness with report issues with transitional movements, such as getting up out of bed. If this muscle does not react fast enough, or in spasms, this can cause these initial changes in position to result in dizziness.
- Visual Vertigo (VV): most patients with VV have more than one type of trigger, and often vertigo has developed, and an associated visual trigger has also developed afterwards. However, this can be easily overlooked as the focus medically may be on the vestibular system, but it is important to also consider associated visual triggers (BPPV may be present, but visual triggers and movements may be contributing to the clinical picture of VV).
Above is only a few of the visual sources of dizziness, and these should be considered with a comprehensive dizziness assessment.
Many clinicians assume that dizziness is only caused by the vestibular system itself, but further testing of visual tracking, acuity, and testing for fixation on a moving and static target should be considered as part of a comprehensive assessment.
Expert opinion by Jessica Povall
This article highlights that many systems, including ocular muscle control, can play a very complex part in the overall picture of steadiness versus dizziness. Often, if a mechanical source of dizziness cannot be found, it is assumed that the patient must be experiencing a psychological trigger to their symptoms.
While a psychological component can ofcourse be present in any case, slowing down and looking further at basic eye movements and functions can shed light more on dizziness. Especially in those with a history of a head injury, or those that have tasks such as focusing on a screen, the risk of more than just an inner ear issue being the root of the dizziness is present and should be further examined.
> From: Chin, Med Hypotheses 116 (2018) 84-95. All rights reserved to Elsevier Ltd. Click here for the online summary.